A. Field of Invention
The invention relates to solar heating systems and to devices for sensing the availability of energy and for providing control signals in response thereto.
B. Description of Prior Art
Solar heating systems which utilize solar heating panels for absorbing solar energy and transferring the energy to a fluid being circulated through the panels are common. Such systems in general require a device for sensing whether or not sufficient energy is available to obtain a transfer of energy in the desired direction and to justify the expenditure of energy in the circulation of the fluid.
Indirect methods and devices employing such methods for sensing the availability of sufficient energy and controlling circulation based on such sensing are in common use. Typical examples are methods and devices: (1) dependent upon the sensing of the temperature of the fluid in the heating panels or the differential temperature between the fluid in the panels and in a storage tank (or at a position in a storage tank) or similar location; and (2) dependent upon the sensing of the air temperature near a solar heating panel or the differential air temperature between a position near the solar heating panel and a position in or near the location where heating is desired.
Sensing and means for sensing the availability of solar energy in a solar heating system is broadly disclosed in Wright U.S. Pat. No. 3,906,928, along with very elementary circuitry; however, the specific embodiment for a sensor which is disclosed apparently is a temperature sensing device--a thermal switch. The use of photosensitive devices in units using solar heat is disclosed in Minnick U.S. Pat. No. 3,981,295 and Harris, Jr. et al U.S. Pat. No. 3,620,206.
Electrical circuits for providing control signals in response to temperature are used in various applications, as shown for example in Futaki U.S. Pat. Nos. 3,583,224, Gardner et al U.S. Pat. No. 3,413,438 and Enders U.S. Pat. No. 3,436,564.